Alt Text Best Practices in SEO

Google's John Mueller shares tips on how to use alt text effectively in the context of SEO.

Google's John Mueller answered a question about how to use alt text for SEO in a Google Office-hours chat. Along the way, he debunked the myth that alt text is limited to 16 characters and offered SEO-friendly suggestions for how to use it.

Alternative Text for Images is referred to as Alt Text. Picture alt text is used to describe what is in an image for those who use a screen reader to view a website.

A screen reader is a type of assistive technology that assists people with visual impairments.

The screen reader reads computer documents aloud so that those who are accessing them can hear what is being written.

Does Google read image alt text with more than 16 words?

John answered a question that had been posed to him.

He said it was from a food blogger:

“Google said that there’s a maximum of 16 words that you can use in your alt text.

And the question is, does Google read the rest of my alt text, and what does this mean for usability?”

Mueller answered the question:

“And I think the important part here is we don’t have any guidelines with regards to how long your alt text can be.

So from a Google Search point of view, you can put a lot of things in the alt text for an image, if that’s relevant for that particular image.”

Is there a limit of 16 words for alternative text?

Image Source

The person who asked the inquiry alluded to what they perceived to be a Google limit of 16 words for alt text.

This concept may have come from an SEO test to see if the text in an image's alt text was searchable in Google Images.

The test employed non-existent terms (basically gibberish) and found that Google couldn't identify photos when searching with more than 16 words.

When you use nonsense to test Google, you're likely to get skewed "SEO test" results.

This is because Google is meant to rank genuine words, not gibberish -  employing gibberish is a bad practice.

So, for gibberish, it's possible that Google will ignore the standard algorithm (because it doesn't apply) and merely try to match the query to the web page, which isn't how Google search generally works.

It's unclear whether that error had an impact on the SEO test.

The argument is that the 16-word limit was determined based on the results of an SEO test, not by Google.

Mueller then went on to explain how Google employs alternative text in photos and what implications that has for how to use alt text for SEO purposes.

Mueller continued his answer:

“When it comes to the alt text, we primarily use that to better understand the image.

So if someone is searching …in Google Images for something that kind of matches the alt text then we can use that to understand that your image is relevant for that alt text on that specific page.

That’s kind of the primary use case of the alt text.

We also use the alt text as a part of the page. But that to me, that’s usually something that is already visible on the page anyway.

So it’s less something that is critical to the page itself.

So I would really use it as something that applies to the image and I would use it for usability and for Google Images to better understand that specific image.”

What Words Should You Use in Your Alt Text?

Mueller then went into detail about how to select the ideal terms for the image alt text.

Mueller continued:

“And I think what might also be worth mentioning is when it comes to Google images, you don’t necessarily need to describe exactly what is in the image.

But rather, kind of like what this image means for your particular page.

So if you have a picture of a beach, you could use an alt text and say, Oh this is a beach.

But you could also say, this is the beach in front of our hotel or this is the beach that we took a photo of when we were doing a chemical cleanup.

And kind of those intents are very different and people would be searching in different ways in Google Images to find more information there. And giving that extra context always makes sense, in my opinion.”

Context can be provided by using alternative text.

When someone using a screen reader comes across a picture on a web page, John Mueller essentially pushes SEOs and publishers to add phrases that provide meaning to the image so that the context of how that image fits into the content of the web page becomes clearer.

If you're unsure what to write in the picture alt text, consider how to describe the image to someone with a visual impairment and then use that description in the alt text.

Learn more about Alt text here.